Chemistry furnace



Oct. 15, 1968 s. ROSIN ET AL 3,406,018

CHEMISTRY FURNACE Filed Dec. 3, 1964 INVENTORS 667M001? Raw/y g Jncx mean United States Patent 3,406,018 CHEMISTRY FURNACE Seymour Rosin, Massapequa Park, and Jack Isreeli,

Mamaroneck, N.Y., assignors to Technicon Corporation, a corporation of New York Filed Dec. 3, 1964, Ser. No. 415,771 8 Claims. (Cl. 23-253) ABSTRACT OF THE DISCLOSURE A chemistry furnace comprises an inner sample receiving tube surrounded by tubular heaters, all enclosed by a tubular reflector, longitudinally divided into two portions, each formed of a glass base element with a reflective metal film on the inner and outer base thereof. The assembly is supported by ceramic end plates which are overlaid by metal end reflectors.

This invention relates to an apparatus for the combustion of materials, and, especially, to a tube furnace for use with a gas analytical system.

Materials are commonly analyzed by combustion by placing the sample to be analyzed in a combustion tube which is then heated to decompose the sample. A catalyst is disposed downstream of the sample to assist in the breaking down of the gases from the combustion, after which the products are passed through absorption agents. An apparatus of this type is shown in the US. Patent No. 3,241,922, issued to Walter Walisch on Mar. 22, 1966.

It is an object of this invention to provide a tube furnace having a minimal heat loss to the surrounding medium or ambient atmosphere.

It is another object of this invention to provide a furnace having an improved reflector structure and sup porting structure therefor.

A feature of this invention is the provision of a reflector formed of an insulator having an interior and an exterior reflective coating thereon.

These and other objects, features and advantages of this invention will become apparent by reference to the following disclosures and the accompanying drawing in which:

FIGURE 1 is a perspective view of a furnace embodying this invention;

FIGURE 2 i a front elevation, in longitudinal section taken along line 22 of FIGURE 1, of the furnace;

FIGURE 3 is an end elevation of the furnace;

FIGURE 4 is a perspective View of the reflectors; and

FIGURE 5 is a longitudinal section taken along line 5-5 of FIGURE 4 of the reflector.

The furnace includes a central glass or ceramic tube into which the sample material is disposed, a plurality of heater rods 12, here shown as four in number, a tubular reflector longitudinally split into an upper reflector 14 and a lower reflector 16, and two end portions which serve to hold the assembly together.

The combustion tube 10 is about one inch in diameter and some twelve inches long. It is heated by the heater rods 12 to a temperature in the order of 900 C. In order to maintain this temperature, power must be supplied to the furnace, in this case by electricity to the heater rods. The amount of power required depends on the heat loss sustained by the furnace. If no heat were lost from the furnace to the surrounding medium, no further power would be required after the required temperature level was attained. As is Well known, heat is transferred in three ways: by conduction, by convection and by radiation. Where the temperature differential is high, as in this case, the transfer by radiation is the most significant. Materials are classified with respect to radiation transfer 3,406,018 Patented Oct. 15, 1968 "ice by how nearly they approach a black body. A perfect black body absorbs all of the radiation incident thereupon, and radiates energy responsive to its temperature according to Plancks radiation equation. A grey body absorbs less and radiates less energy. A perfect reflector neither absorbs nor radiates energy. To obtain a minimum heat transfer by radiation the furnace is therefore enclosed by as perfect a reflector as can be achieved economically.

The furnace is enclosed by a tubular reflector, made in two portions 14 and 16, about 3 /2 inches in diameter. The tube is made of a sheet of glass 18 and is provided with a reflective coating 20 on its inner surface. This coating is chosen to be highly eificient in the infra-red wavelengths and able to withstand the high temperatures involved. Gold and rhodium are exemplary of suitable materials; and may be vapor deposited on the glass as a film.

Radiation travelling outwardly from the center of the furnace strikes the inner reflective coating 20 and about 98% of this radiant heat is reflected back inwardly. The remaining heat will be absorbed by the coating and transferred to the glass 18. Additional heat will be transferred to the coating 20 by conduction and convection and thence to the glass. As a result, the glass would assume a temperature intermediate that of the furnace and the surrounding medium. Glass is a grey body and is capable, therefore, of radiating appreciable quantities of heat to the surrounding medium. We have discovered that we can minimize the radiation loss from the glass to the surrounding medium by providing the glass with an outer reflective coating 22 similar to the inner coating 20. This coating significantly reduces the grey body radiation of the glass, which constitutes the major form of heat loss therefrom. I

The end portions of the furnace each include a ceramic disc 26 having a peripheral slot 28 therein, dividing the disc into an inner portion 30 and an outer portion 32. The inner portion 30 has a uniform radius. The outer portion 32 has three recesses 34, 36 and 38 which are radially coextensive with the peripheral slot 28. An annular disc 40, which may be made of aluminum, is mounted onto the disc 26 in the slot 28 by means of three inward going projections 42, 44 and 46. The recesses 34, 36 and 38 of the ceramic disc and the projections 42, 44 and 46 of the annular disc interengage in the manner of a bayonet lock. Each of the two annular discs 40 has a double tab 48 fixed thereto by a pair of nuts 50 and bolts 52, and this tab- 48 is fixed to an upright support 54, which thus holds the annular disc in a vertical plane. The two supports 54 are mounted to a base not shown, at a given spacing apart. Each disc also has two tabs 56 and 58 fixed thereto by similar nuts and bolts, each having a horizontally inwardly bent portion 56A and 58A respectively. Each end of the lower reflector portion 16 is disposed between the periphery of the annular disc 40 and the bent portions of the lower tabs 56A and 58A. Each annular disc also has an upper tab 60 fixed thereto by a nut and bolt 61 and 63. The upper reflector portion is supported on its downward facing edges 62 and 64 by the upward facing edges 66 and 68 of the lower portion 16, by the upper peripheries of the annular discs 40. and held between the two tabs 60.

Each ceramic disc 26 has a central aperture 70 which receives and supports the combustion tube 10. Each disc also has four radially spaced apart bolts 72 which receive and support the ends of the four heater rods 12. Each hole 72 has an inwardly directed step recess 74 so that the respective rod 12 may pass through the hole 72 and then fall into the recess 74. Each heater rod 12 consists of a glass or ceramic tube having an electric resistance wire 76 therein. The ends of the resistance wires pass out through the tubes, the holes 72, and are fixed to terminals 78, to which the input power conductors 80 are also fixed. Two additional end plate assemblies may be disposed outside of the furnace spaced from each end plate 40. These plates may have reflective inner surfaces to reflect any heat radiated out of the furnace from the end plates 26 and 40. Each end plate assembly is formed of two substantially semicircular aluminum plates 82 and 84. The two plates are pivotally mounted to an extension 61A of the bolt 61. The straight edges of the two plates overlap, except at the pivot remote portions thereof which are exactly on the diameter and are bent slightly inwardly and outwardly respectively to form abutting surfaces, and at the medial portions thereof which are cut out to encircle the central tube 10.

While this foregoing embodiment has been described as a combustion furnace operating at about 900 C., it will be appreciated that it may similarly be embodied as a reduction furnace operating at about 600 C.

While we have shown and described the preferred embodiment of the invention, it will be understood that the invention may be embodied otherwise than as herein specifically illustrated or described and that certain changes in the form and arrangement of parts and in the specific manner of practicing the invention may be made without departing from the underlying idea or principles of this invention within the scope of the appended claims.

What is claimed is:

1. A furnace comprising: a receptacle for supporting material to be heated; power means for supplying heat to said receptacle; and a reflector, substantially enclosing said receptacle and said power means, said reflector including a base element, an inner reflective coating thereon, and an outer reflective coating thereon.

2. A furnace comprising: a tubular receptacle for supporting material to be heated; power means for supplying heat to said receptacle; and a tubular reflector, substantially enclosing said receptacle and said power means, said tubular reflector including a ceramic element, an inner reflective metal film thereon, and an outer reflective metal film thereon.

3. A furnace comprising: a tubular receptacle for supporting material to be heated; power means for supplying heat to said receptacle; and a tubular reflector, substantially enclosing said receptacle and said tubular reflector longitudinally divided into two symmetrical portions, each including a ceramic element, an inner reflective metal film thereon, and an outer reflective metal film thereon.

4. A furnace comprising: two fixedly spaced apart ceramic end plates, each end plate having a central aperture and a plurality of additional apertures; a tube disposed through, between and extending beyond said central apertures for supporting material to be heated; power means disposed within and between said additional apertures; a tubular reflector, longitudinally divided into two symmetrical portions, each including a ceramic element, an inner reflective metal coating thereon, and an outer reflective metal coating thereon; two support means, each securing one end of said reflector to a respective one of said end plates.

5. A furnace comprising: two fixedly spaced apart ceramic end plates, each end plate having a central aperture and a plurality of additional apertures; a tube disposed through, between and extending beyond said central apertures for supporting material to be heated; power means disposed within and between said additional apertures; a tubular reflector, longitudinally divided into two symmetrical portions, each including a ceramic element, an inner reflective metal coating thereon, and an outer reflective metal coating thereon; and two support means, each securing one end of said reflector to a respective one of said end plates; and two additional reflector means, each disposed beyond a respective end plate and passing said tube therethrough.

6. A furnace comprising: two fixedly spaced apart ceramic end plates, each end plate having a central aperture and a plurality of additional apertures; a tube disposed through, between and extending beyond said central apertures for supporting material to be heated; elongated heating elements disposed within and between said additional apertures; a tubular reflector, longitudinally divided into two symmetrical portions, each including a ceramic element, an inner reflective metal coating thereon, and an outer reflective metal coating thereon; two annular end plates, each disposed on a respective one of said ceramic end plates, and securing a respective one end of said reflector thereto.

7. A furnace comprising: two fixedly spaced apart ceramic end plates, each end plate having a central aperture and a plurality of additional apertures; a tube disposed through, between and extending beyond said central apertures for supporting material to be heated; elongated heating elements disposed within and between said additional apertures; a tubular reflector, longitudinally divided into two symmetrical portions, each including a ceramic element, an inner reflective metal coating thereon, and an outer reflective metal coating thereon; and two annular end plates, each disposed on a respective one of said ceramic end plates, and securing .a respective one end of said reflector thereto; and two additional reflector plates, each divided into two portions, pivotally mounted to and disposed beyond a respective one of said annular end plates.

8. A furnace comprising: two fixedly spaced apart ceramic end plates, each end plate having a central aperture and a plurality of additional apertures; a tube disposed through, between and extending beyond said central apertures for supporting material to be heated; elongated heating elements disposed within and between said additional apertures; a tubular reflector, longitudinally divided into two symmetrical portions, each including a ceramic element, an inner reflective metal coating thereon, and an outer reflective metal coating thereon; two annular end plates, each disposed on a respective one of said ceramic end plates, and having a plurality of tabs for securing a respective One end of said reflector thereto.

References Cited UNITED STATES PATENTS 2,060,136 11/1936 Summey 13-26 2,787,457 4/1957 Bogdan 263-41 1,816,476 7/1931 Fink et al. 117-35 2,322,159 6/1943 Saxer et al 23-253 2,422,609 6/ 1947 Avw'zirter 9l-70.1 2,464,256 3/ 1949 Packer 88-105 2,954,826 10/1960 Sievers 166-60 3,105,772 10/1963 Loiseleur 117-35 3,241,922 3/1966 Walisch 23-253 MORRIS O. WOLK, Primary Examiner. E. A. KATZ, Assistant Examiner. 

